Substrate processing method

ABSTRACT

A substrate processing method capable of achieving uniform etch selectivity in the entire thickness range of a thin film formed on a stepped structure includes: forming a thin film on a substrate by performing a plurality of cycles including forming at least one layer and applying plasma to the at least one layer under a first process condition; and applying plasma to the thin film under a second process condition different from the first process condition.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 62/906,085, filed on Sep. 25, 2019, and U.S. Provisional Application No. 63/054,220, filed on Jul. 20, 2020, in the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND 1. Field

One or more embodiments relate to a substrate processing method, and more particularly, to a substrate processing method that may improve the etch selectivity of a thin film formed on a stepped structure.

2. Description of Related Art

As semiconductor pattern structures are miniaturized and made three-dimensional, there is an increasing need for new thin film deposition techniques that may simplify the process. For example, a 3D NAND flash device has a vertically stacked gate structure and an electrode wiring structure. In order to interconnect these structures, a technique of selectively removing a film deposited on a stepped structure to form a pad structure is required.

In order to selectively remove the film deposited on the stepped structure, the film is deposited on the stepped structure through a plasma process, and then wet-etched to remove a side film of the stepped structure, leaving upper and lower films of the stepped structure. However, a method of removing the upper and lower films of the stepped structure and leaving the side film of the stepped structure may also be used.

This method is possible by controlling plasma to be applied and adjusting characteristics of the upper and lower films or the side film of the stepped structure. For example, the side film may be removed during etching by using the straightness of radicals to make the upper and lower films in the direction perpendicular to the direction of radical progression to be harder than the side film. Conversely, by increasing the intensity of the plasma to strengthen ion bombardment, a bonding structure of the upper film and the lower film may be weakened rather than the side film to remove the upper film and the lower film during etching.

This process may be accomplished by varying plasma application conditions. For example, below a certain plasma power or plasma density, thin film densification may be dominant on a thin film surface perpendicular to the direction of radical progression. Conversely, above a certain plasma power or plasma density, a thin film bonding structure may be weakened on the thin film surface perpendicular to the direction of radical progression.

SUMMARY

One or more embodiments include a substrate processing method that may improve the etch selectivity of a thin film by achieving uniform etch selectivity in the entire thickness range of the thin film formed on a stepped structure.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the disclosure.

According to one or more embodiments, a substrate processing method includes: forming a thin film on a substrate by performing a plurality of cycles including forming at least one layer and applying plasma to the at least one layer under a first process condition to the layer; and applying plasma to the thin film under a second process condition different from the first process condition.

According to an example of the substrate processing method, an atmosphere may be set such that plasma ions have directionality during the applying of the plasma under the first process condition and during the applying of the plasma under the second process condition.

According to another example of the substrate processing method, a bonding structure of a portion of the thin film may be changed during the applying of the plasma under the first process condition, and the bonding structure of a portion of the thin film may be further changed during the applying of the plasma under the second process condition.

According to another example of the substrate processing method, the substrate processing method further includes an isotropic etching operation, wherein etch selectivity between the portion where the bonding structure of the thin film is changed and the remaining portion of the thin film may be achieved during the isotropic etching operation.

According to another example of the substrate processing method, the at least one layer may be formed on a stepped structure having an upper surface, a lower surface, and a side surface between the upper surface and the lower surface, and the portion of the thin film may correspond to a portion of the thin film formed on the upper surface and the lower surface.

According to another example of the substrate processing method, repetition of the above cycles causes a difference between a first bonding structure of a first portion of the thin film adjacent to the stepped structure and a second bonding structure of a second portion of the thin film away from the stepped structure, and during the applying of the plasma under the second process condition, the difference between the first bonding structure of the first portion and the second bonding structure of the second portion may be reduced.

According to another example of the substrate processing method, the substrate processing method may further include an isotropic etching operation. After the isotropic etching operation, thin films on the upper surface and the lower surface of the stepped structure may be removed, and a thin film on the side surface of the stepped structure may remain.

According to another example of the substrate processing method, a hydrogen-containing gas may be supplied during the applying of the plasma under the second process condition.

According to another example of the substrate processing method, the forming of the at least one layer may include: supplying a first gas; purging the first gas; and supplying a second gas and applying plasma to form a first layer.

According to another example of the substrate processing method, pressure in a reaction space is maintained at a first pressure during the supplying of the second gas and applying the plasma to form the first layer, and the pressure in the reaction space may be maintained at a second pressure lower than the first pressure during the applying of the plasma under the first process condition.

According to another example of the substrate processing method, power supplied during the applying of the plasma under the first processing condition is greater than power supplied during the supplying of the second gas and the applying of the plasma to form the first layer.

According to another example of the substrate processing method, the first gas may be supplied during the applying of the plasma under the second process condition that is different from the first process condition.

According to another example of the substrate processing method, during a first cycle, the supplying of the first gas, the purging of the first gas, and the supplying of the second gas and applying of plasma to form the second layer may be performed a plurality of times.

According to another example of the substrate processing method, during the first cycle, the plasma under the first process condition is applied to the first layer so that a WER of a portion of the first layer may increase due to an ion bombardment effect of the plasma ions.

According to another example of the substrate processing method, forming of a second layer on the first layer during a second cycle after the first cycle is performed, wherein the forming of the second layer may include: supplying the first gas; purging the first gas; and supplying the second gas and applying the plasma to form the second layer.

According to another example of the substrate processing method, during the second cycle, the plasma under the first process condition is applied to the second layer and the first layer which is below the second layer so that WERs of a portion of the first layer and a portion of the second layer may increase due to an ion bombardment effect of the plasma ions, wherein the WER of the first layer may be greater than the WER of the second layer.

According to another example of the substrate processing method, the plasma under the second process condition is applied toward the first layer and the second layer, and thus the difference between the WER of the first layer and the WER of the second layer may be reduced.

According to one or more embodiments, a substrate processing method includes: forming a first layer; applying first plasma to the first layer to change characteristics of a portion of the first layer; forming a second layer on the first layer; applying second plasma to the first layer and the second layer to change characteristics of respective portions of the first layer and the second layer; and applying third plasma to the second layer to reduce a difference between the characteristics of the portion of the first layer and the characteristics of the portion of the second layer.

According to an example of the substrate processing method, a first process condition may be used during the application of the first plasma and the application of the second plasma, and a second process condition that is different from the first process condition may be used during the application of the third plasma.

According to one or more embodiments, a substrate processing method includes: forming a thin film on a substrate by performing a cycle including supplying a first gas onto a substrate and supplying a second gas having reactivity with the first gas a plurality of times, wherein, due to repetition of the cycle, a first portion of the thin film adjacent to the substrate has a higher WER than that of a second portion of the thin film away from the substrate; and reducing a difference between the WER of the first portion and the WER of the second portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a flowchart of a substrate processing method according to embodiments;

FIG. 2 is a view of a substrate processing method according to embodiments;

FIG. 3 is a view of a substrate processing method according to embodiments;

FIG. 4 is a view of a substrate processing device in which a substrate processing method is performed;

FIG. 5 is a view of a thin film formed on a stepped structure and a film remaining after isotropic etching;

FIG. 6 is a view of a substrate processing method according to embodiments;

FIG. 7 is a graph showing a change in a wet etch rate in a thin film;

FIG. 8 is a view of a state in which a thin film formed on a stepped structure remains after isotropic etching;

FIG. 9 is a view of a substrate processing method according to embodiments;

FIG. 10 is a graph showing etching characteristics of a thin film after a process according to the disclosure;

FIG. 11 is a view of the etch selectivity of a thin film obtained according to different substrate processing methods;

FIG. 12 is a view of a substrate processing method according to embodiments;

FIG. 13 is a view of a substrate processing method according to embodiments;

FIG. 14 is a view of a substrate processing method according to embodiments;

FIG. 15 is a view of a state in which a thin film formed by the above-described substrate processing methods remains after isotropic etching;

FIG. 16 illustrates a substrate processing method according to embodiments of the disclosure; and

FIGS. 17A and 17B illustrate a degree of wet etching of a thin film on a sidewall of a pattern structure according to the presence or absence of plasma purging in accordance with examples of the disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

It will be understood that, although the terms first, second, etc. may be used herein to describe various members, components, regions, layers, and/or sections, these members, components, regions, layers, and/or sections should not be limited by these terms. These terms do not denote any order, quantity, or importance, but rather are only used to distinguish one component, region, layer, and/or section from another component, region, layer, and/or section. Thus, a first member, component, region, layer, or section discussed below could be termed a second member, component, region, layer, or section without departing from the teachings of embodiments.

In the disclosure, “gas” may include evaporated solids and/or liquids and may include a single gas or a mixture of gases. In the disclosure, a process gas introduced into a reaction chamber through a shower head may include a precursor gas and an additive gas. The precursor gas and the additive gas may typically be introduced as a mixed gas or may be separately introduced into a reaction space. The precursor gas may be introduced together with a carrier gas such as an inert gas. The additive gas may include a dilution gas such as a reaction gas and an inert gas. The reaction gas and the dilution gas may be mixedly or separately introduced into the reaction space. The precursor may include two or more precursors, and the reaction gas may include two or more reaction gases. The precursor may be a gas that is chemisorbed onto a substrate and typically contains metalloid or metal elements constituting a main structure of a matrix of a dielectric film, and the reaction gas for deposition may be a gas that is reactive with the precursor chemisorbed onto the substrate when excited to fix an atomic layer or a monolayer on the substrate. The term “chemisorption” may refer to chemical saturation adsorption. A gas other than the process gas, that is, a gas introduced without passing through the shower head, may be used to seal the reaction space, and it may include a seal gas such as an inert gas. In some embodiments, the term “film” may refer to a layer that extends continuously in a direction perpendicular to a thickness direction without substantially having pinholes to cover an entire target or a relevant surface, or may refer to a layer that simply covers a target or a relevant surface. In some embodiments, the term “layer” may refer to a structure, or a synonym of a film, or a non-film structure having any thickness formed on a surface. The film or layer may include a discrete single film or layer or multiple films or layers having some characteristics, and the boundary between adjacent films or layers may be clear or unclear and may be set based on physical, chemical, and/or some other characteristics, formation processes or sequences, and/or functions or purposes of the adjacent films or layers.

In the disclosure, the expression “containing an Si—N bond” may be referred to as characterized by an Si—N bond or Si—N bonds having a main skeleton substantially constituted by the Si—N bond or Si—N bonds and/or having a substituent substantially constituted by the Si—N bond or Si—N bonds. A silicon nitride layer may be a dielectric layer containing a Si—N bond, and may include a silicon nitride layer (SiN) and a silicon oxynitride layer (SiON).

In the disclosure, the expression “same material” should be interpreted as meaning that main components (constituents) are the same. For example, when a first layer and a second layer are both silicon nitride layers and are formed of the same material, the first layer may be selected from the group consisting of Si2N, SiN, Si3N4, and Si2N3 and the second layer may also be selected from the above group but a particular film quality thereof may be different from that of the first layer.

Additionally, in the disclosure, according as an operable range may be determined based on a regular job, any two variables may constitute an operable range of the variable and any indicated range may include or exclude end points. Additionally, the values of any indicated variables may refer to exact values or approximate values (regardless of whether they are indicated as “about”), may include equivalents, and may refer to an average value, a median value, a representative value, a majority value, or the like.

In the disclosure where conditions and/or structures are not specified, those of ordinary skill in the art may easily provide these conditions and/or structures as a matter of customary experiment in the light of the disclosure. In all described embodiments, any component used in an embodiment may be replaced with any equivalent component thereof, including those explicitly, necessarily, or essentially described herein, for intended purposes, and in addition, the disclosure may be similarly applied to devices and methods.

Hereinafter, embodiments of the disclosure will be described with reference to the accompanying drawings. In the drawings, variations from the illustrated shapes may be expected as a result of, for example, manufacturing techniques and/or tolerances. Thus, the embodiments of the disclosure should not be construed as being limited to the particular shapes of regions illustrated herein but may include deviations in shapes that result, for example, from manufacturing processes.

FIG. 1 is a flowchart of a substrate processing method according to embodiments of the present invention.

Referring to FIG. 1 , the substrate processing method may include operation S110 of forming at least one layer and operation S120 of applying plasma under a first process condition. Operations S110 and S120 may be repeated a plurality of times as one group-cycle, and a thin film may be formed on a substrate by the repetition. The substrate processing method may further include operation S150 of applying plasma under a second process condition different from the first process condition.

During operation S110 of forming at least one layer, a thin film may be formed on a stepped structure. That is, the thin film may be formed on the stepped structure having an upper surface, a lower surface, and a side surface between the upper surface and the lower surface. The stepped structure may be a structure having a high aspect ratio, and the aspect ratio may be, for example, greater than or equal to width:height=1:10. To form a conformal thin film on the stepped structure with such a high aspect ratio, an atomic layer deposition (ALD) process may be used. In particular, a plasma atomic layer deposition process (PEALD) may be used.

During operation S110 of forming at least one layer, the atmosphere may be set such that an average free path of plasma ions is reduced and the plasma ions are not directional (i.e., such that random movement of the plasma ions is increased). Such an atmosphere may contribute to forming a conformal thin film on a stepped structure with a high aspect ratio. In order to achieve the above atmosphere, a high pressure atmosphere (e.g., 10 to 20 Torr) may be formed. In another embodiment, in order to achieve the above atmosphere, a low power atmosphere (e.g., 200 W to 500 W) may be formed. In another embodiment, in order to achieve the above atmosphere, a high temperature atmosphere may be formed.

During operation S110 of forming of at least one layer, a layer may be formed using plasma. For example, operation S110 may include supplying a first gas, purging the first gas, and supplying a second gas and applying plasma to form a first layer. By applying the plasma, a second gas may be excited to become reactive, and the reactive second gas may react with the first gas to form the first layer.

The first gas may include a material that is chemisorbed on the substrate as a source gas. The second gas may include a material reactive with the first gas, in particular a material reactive with the first gas under a plasma atmosphere. In an alternative embodiment, the supplying of the second gas and the applying of the plasma may be performed simultaneously. In another embodiment, after the supplying of the second gas, the applying of the plasma may be performed.

Operation S110 of forming at least one layer may be performed a plurality of times (e.g., a cycles). In more detail, a group-cycle GC including operation S110 of forming at least one layer and operation S120 of applying the plasma under the first process condition may be performed a plurality of times. Operation S110 of forming at least one layer may be performed a plurality of times during one group-cycle GC. Therefore, during one cycle, the supplying of the first gas, the purging of the first gas, and the supplying of the second gas and the applying of plasma to form the second layer, which are included in operation S110 of forming at least one layer, may be performed a plurality of times.

After operation S110 of forming at least one layer, operation S120 of applying the plasma under the first process condition is performed. Operation S120 of applying the plasma under the first process condition may be performed for a certain time (e.g., b seconds). By applying the plasma under the first process condition, a bonding structure of a portion of the at least one layer may be changed. During operation S120 of applying the plasma under the first process condition, the plasma ions may be set to be directional. On the other hand, as described above, during operation S110 of forming the at least one layer, the plasma ions may be set to have no directionality.

The directional plasma ions may change a bonding structure of a portion of the thin film. For example, in a case where a thin film is formed on a stepped structure having an aspect ratio, the directivity of plasma ions may be set to face an upper surface or a lower surface of the stepped structure. In this case, the plasma ions may change a bonding structure of a thin film formed on the upper or lower surface of the stepped structure. In contrast, the directional plasma ions may not affect a bonding structure of a thin film formed on the side of the stepped structure.

As described above, in operation S110 of forming at least one layer, the pressure in a reaction space may be maintained at a first pressure (e.g., a high pressure) while supplying the second gas and applying the plasma so that random movement of the reaction gas may be increased. In contrast, in operation S120 of applying the plasma under the first process condition, the pressure in the reaction space may be maintained at a second pressure (e.g., a lower pressure) less than the first pressure so that the movement of the reaction gas is directional.

Furthermore, in operation S110 of forming at least one layer, power supplied during operation S110 may be maintained at a first power value (e.g., a low power value) so that the reaction gas is less affected by the power (i.e., the plasma ions become not directional). In contrast, in operation S120 of applying the plasma under the first process condition, power supplied during operation S120 may be maintained at a second power value (e.g., a high power value) that is higher than the first power value so that the reaction gas is more affected by the power (i.e., the plasma ions become directional).

Operation S110 of forming at least one layer and operation S120 of applying the plasma under the first process condition may be defined as one group-cycle GC, and the group-cycle GC may be repeatedly performed. In other words, in operation S100, the X value is set to 1 before performing the group-cycle GC, and in operation S140, after performing the group-cycle GC including operation S110 of forming at least one layer and operation S120 of applying the plasma under the first process condition, the X value is increased, and when the X value reaches a certain value in operation S130, the group-cycle GC is terminated and subsequent operations may be performed.

As a subsequent operation, operation S150 of applying plasma under the second process condition is performed. Operation S150 of applying the plasma under the second process condition may be performed for a certain time (e.g., y seconds). By applying the plasma under the second process condition, a bonding structure of a portion of the at least one layer may be further changed. During operation S150 of applying the plasma under the second process condition, the plasma ions may be set to be directional.

For example, the plasma ions may be set to be directed towards at least one layer. In this case, since plasma ions are incident at least towards the layer, a portion where the bonding structure of the at least one layer is changed will be a portion formed on upper and lower surfaces of a pattern structure. When power of the plasma is above a threshold value, portions formed on an upper surface and a lower surface of the at least one layer will be weakened, and when power of the plasma is below a threshold value, portions formed on an upper surface and a lower surface of the at least one layer will be dense.

Both operation S120 of applying the plasma under the first process condition and operation S150 of applying the plasma under the second process condition are common in that they change the bonding structure of the thin film. However, since the first process condition and the second process condition are different, a thickness range of a thin film which bonding structure is changed by the first process condition is different from a thickness range of a thin film which bonding structure is changed by the second process condition.

In more detail, when a cycle including operation S110 of forming at least one layer and operation S120 of applying the plasma under the first process condition is repeated, in the case of initially formed layers (i.e., a first portion of a thin film adjacent to the stepped structure), changes in the bonding structure due to the plasma application may be accumulated. Meanwhile, in the case of later formed layers (i.e., a second portion of a thin film away from the stepped structure), only a few plasma applications (or one plasma application) are performed, so the change in the bonding structure may be relatively less.

To offset this partial difference in the bonding structure, the plasma under the second process condition may be applied. For example, the plasma under the second process condition may be applied to cause a change in the bonding structure of the second portion of the thin film away from the stepped structure and to not affect the bonding structure of the first portion of the thin film adjacent to the stepped structure. By applying the plasma under the second process condition, a difference between the bonding structure of the first portion and the bonding structure of the second portion may be reduced.

In an embodiment, a hydrogen-containing gas may be supplied during operation S150 of applying the plasma under the second process condition. By performing plasma treatment using the hydrogen-containing gas, more Si—H bonds may be formed in the second portion of the thin film away from the stepped structure. Therefore, the etch rate of a corresponding portion may be increased in the subsequent etching process.

In another embodiment, the same gas as the gas supplied in operation S150 of forming at least one layer may be supplied during operation S150 of applying the plasma under the second process condition. For example, supplying a first gas (e.g., the source gas), purging the first gas, and supplying a second gas (e.g., the reaction gas) and applying the plasma to form the first layer may be performed during operation S110 of forming at least one layer. The first gas (e.g., the source gas) may be supplied during operation S150 of applying the plasma under the second process condition.

In this case, a thin film may be additionally formed on a side surface of a stepped structure while maintaining an ion bombardment effect on the surfaces of thin films formed on an upper surface and a lower surface of the stepped structure by the applying of the plasma under the second process condition. This is particularly advantageous in the case of weakening a bonding structure of a thin film because a thin film is further formed on the side surface of the stepped structure while the thin films formed on the upper surface and the lower surface are weakened by the directional plasma, thereby increasing the etch selectivity. Furthermore, due to the source gas supplied during the plasma application, an ion bombardment effect of the plasma ions on the thin film formed on the side surface may be reduced.

After operation S150 of applying the plasma under the second process condition, operation S160 of isotropic etching on a thin film formed by performing a plurality of group-cycles is performed. For example, wet etching of the thin films may be performed. For example, wet etching may be performed by immersing a substrate on which a semiconductor device, such as a thin film, is deposited, in a liquid etching solution and etching the surface by a chemical reaction. Since such wet etching is isotropic etching, such isotropic etching itself may not significantly affect elective etching of the thin film formed on the stepped structure.

During operation S160 of isotropic etching, the etch selectivity between a portion where a bonding structure of the thin film is changed and the remaining portion of the thin film may be achieved. In other words, by performing operation S120 of applying the plasma under the first process condition and operation S150 of applying the plasma under the second process condition, the bonding structure of a portion of the thin film (the thin films on the upper and lower surfaces of the stepped structure) on the stepped structure is changed, so that a portion of the thin film may be removed and other portions may remain during the isotropic etching. By removing a portion of the thin film on the stepped structure, a surface of the stepped structure may be exposed. Therefore, selective etching of the thin film may be achieved by a subsequent etching process. Thus, a patterned thin film formed on an area of a stepped structure may be formed without a separate additional photolithography process.

According to embodiments of the inventive concept, a combination of operation S120 of applying the plasma under the first process condition and operation S150 of applying the plasma under the second process condition different from the first process condition are used. By combining and applying plasmas having such different process conditions, it is possible to achieve uniform etch selectivity over the entire thickness range of the thin film formed on the stepped structure, compared to a case where only plasma of a one-type process condition is applied.

When only operation S120 of applying the plasma under the first process condition is performed, as the cycle is repeated, an area where plasma is applied several times occurs. Therefore, the etch selectivity increases in a deep portion of the thin film by applying the plasma several times, whereas the etch selectivity decreases relatively in a surface of the thin film. With low etch selectivity at the surface, productivity is reduced because a thickness of the thin film needs to be deposited thicker than a target thickness in order to form a side film of an appropriate thickness.

When only operation S150 of applying the plasma under the second process condition is performed, a high etch selectivity may be achieved by an ion bombardment effect and/or penetration of active species (e.g., hydrogen ions) into the thin film. However, the possibility of defects in the substrate is increased by the bombardment effect and the penetration of active species. In order to prevent this, when a plasma power is reduced or a penetration force of the active species is lowered, the problem that etch selectivity at the deep portion (i.e., the portion adjacent to the stacked structure and/or the substrate) of the thin film is lowered occurs. As a result, the thickness of the thin film needs to be deposited thicker than the target thickness in order to form a side film of an appropriate thickness, thereby reducing productivity.

By performing the combination of operation S120 of applying the plasma under the first process condition and operation S150 of applying the plasma under the second process condition different from the first process condition, the disadvantages of each of them may be complemented. In other words, by the combination, a markedly improved effect may be achieved compared to the case of performing only an individual plasma application process.

A change in the bonding structure of a portion of the thin film by plasma ions may be weakening of the bonding structure, or may be densification of the bonding structure. Hereinafter, embodiments will be described in more detail on the premise of the weakening the bonding structure.

An atmosphere may be set such that plasma ions have directionality during operation S120 of applying plasma under the first process condition and operation S150 of applying the plasma under the second process condition. The binding structure of a portion of the thin film may be weakened by the ion bombardment effect of the directional plasma ions.

In more detail, the plasma ions may have a direction perpendicular to the upper and lower surfaces of the stepped structure. Therefore, the bonding structure of the upper and lower surfaces of the thin film may be weakened. As a result, by the subsequent operation S160 of isotropic etching, the thin films on the upper surface and the lower surface of the stepped structure may be removed, and a thin film on the side surface of the stepped structure may remain.

During a first group-cycle, operation S110 of forming at least one layer may be performed to have a plurality of sub cycles. During the individual sub cycles, supplying a first gas, purging the first gas, and supplying a second gas and applying plasma to form a first layer may be performed.

During the first group-cycle and after the sub cycles, the plasma under the first process condition may be applied for a certain time. By applying the plasma under the first process condition to the first layer, a wet etch rate (WER) of a portion of the first layer may increase due to the ion bombardment effect of the plasma ions.

This ends the first group-cycle and starts the second group-cycle. During the second group-cycle, operation S110 of forming at least one layer may be performed to have a plurality of sub cycles. A second layer formed during the second group-cycle will be formed on the first layer. During the individual sub cycle of the second group-cycle, supplying a first gas, purging the first gas, and supplying a second gas and applying plasma to form the second layer may be performed.

During the second group-cycle and after the sub cycle for forming the second layer, the plasma under the first process condition may be applied for a certain time. By applying the plasma under the first process condition to the second layer, a WER of a portion of the second layer may increase due to the ion bombardment effect of the plasma ions. Meanwhile, the applied plasma may affect not only the second layer but also the first layer below the second layer. Thus, the WER of a portion of the first layer may further increase, and consequently the WER of the first layer may be greater than the WER of the second layer.

After the first group-cycle and the second group-cycle, the plasma under the second process condition may be applied toward the first layer and the second layer. As described above, the second process condition may be different from the first process condition. In particular, the second process condition may be a process condition that weakens the second layer of the upper portion but does not significantly affect the first layer of the lower portion. For example, the second process conditions may produce an active species having low penetration, and the active species may only weaken the upper second layer and not significantly affect the weakening of the lower first layer. As a result, by applying the plasma of the second process, the difference between the WER of the first layer and the WER of the second layer may be reduced.

Although it is described in this disclosure that the plasma under the second process condition is applied after the second group-cycle, an additional group-cycle may be performed between the second group-cycle and the plasma application under the second process condition. For example, a third group-cycle may be performed after the second group-cycle. During the third group-cycle, operation S110 of forming at least one layer may be performed to have a plurality of sub cycles. A third layer formed during the third group-cycle will be formed on the first layer and the second layer.

Subsequently, the plasma under the first process condition is applied to the third layer, and due to the ion bombardment effect of the plasma ions, WERs of portions (portions on an upper surface and a lower surface of the stepped structure) may increase (see FIG. 6 ). As the cycle repeats, the first portion (e.g., the first layer) of the thin film adjacent to the substrate will have a higher WER than that of the second portion (e.g., the second layer) of the thin film away from the substrate.

The plasma application under the second process condition performed after the group-cycle is performed for the purpose of reducing the difference in the WERs. In other words, by repeating the group-cycle, the plasma under the first process condition is repeatedly applied to increase the etch selectivity of the deep portion of the thin film, whereas the etch selectivity of the surface of the thin film is lowered. Therefore, the plasma under the second process condition is applied to solve this problem. By applying the plasma under the second process condition, the etch selectivity of the surface of the thin film may be increased, and thus uniform etch selectivity may be achieved regardless of the thickness (or depth) of the thin film.

FIG. 2 is a view of a substrate processing method according to embodiments. The substrate processing method according to the embodiments may be a variation of the substrate processing method according to the above-described embodiments. Hereinafter, repeated descriptions of the embodiments will not be given herein.

According to embodiments of the inventive concept, a substrate processing method may be proposed to increase the WERs of films deposited on the upper portion and the lower portion of the stepped structure and to make the WERs constant over time. For example, a first sub-step of evenly depositing a hard and uniform thin film on the stepped structure, and a second sub-step of performing plasma treatment to increase the etch selectivity of thin films deposited on a side portion, upper portion, and lower portion of the stepped structure, and a third sub-step of performing plasma treatment using a hydrogen-containing gas (e.g., H2) may be performed.

Referring to FIG. 2 , during the first sub-step (Step 1), a hard and uniform SiN film is evenly deposited on the stepped structure. For example, the SiN film may be deposited by plasma atomic layer deposition. The first sub-step (Step 1) may be repeated a times and an SiN film having a certain thickness may be formed. During the second sub-step (Step 2), plasma treatment is performed for b seconds (sec). The first sub-step and the second sub-step are made into one group-cycle, and the film is repeatedly deposited a plurality of times (x cycles) according to a required thickness. In the first sub-step (Step 1), a high process pressure and a low plasma power are applied to weaken the directivity (straightness) of a plasma active species and evenly deposit a hard and uniform SiN film in the stepped structure. In the second sub-step (Step 2), the etch selectivity of the thin films deposited on the side portion, upper portion, and lower portion of the stepped structure is increased by supplying a low process pressure and a high plasma power to enhance the directivity (straightness) of the plasma active species.

The third sub-step (Step 3) is a plasma treatment step using a hydrogen-containing gas, which is maintained for y seconds (sec). The low pressure and the high plasma power are maintained so that H ions produced by the hydrogen-containing gas easily penetrate into the film. The H ions may form weak bonding with SiN or weaken an Si—N bonding structure. The weakening of the bonding structure by the H ions may maximize the effect at a surface where the plasma treatment is directly performed. Here, a low H2 flow rate is maintained to prevent pile-up of the H ions (i.e., to prevent weakening of the thin film in the deep portion). For example, in the third sub-step (Step 3), the H2 flow rate may be performed under a condition of 100 sccm or less. The third sub-step (Step 3) is a step of adjusting the etch selectivity at a surface of the deposited film to be similar to the etch selectivity at the deep portion of the deposited film.

In an alternative embodiment, in the plasma treatment of the third sub-step (Step 3), in addition to the hydrogen-containing gas, other gases that can be easily penetrated into the film may be used. Gases such as He to Ar may be used. Wet etching is then performed to retain an SiN film on a sidewall and remove the SiN films on an upper wall and a lower wall.

FIG. 3 is a view of a substrate processing method according to embodiments. FIG. 4 is a view of a substrate processing device in which a substrate processing method is performed. The substrate processing method according to the embodiments may be a variation of the substrate processing method according to the above-described embodiments. Hereinafter, repeated descriptions of the embodiments will not be given herein.

Referring to FIG. 4 , the substrate processing device may include at least one reactor. An upper electrode connected to an RF generator, for example, a showerhead and a lower electrode disposed opposite to the upper electrode may be disposed in the reactor. A substrate may be loaded on the lower electrode, such as a heater block, and a plasma process may be performed on the substrate. In some embodiments, the reactor may be a direct plasma reactor.

A layer formed on the substrate using the substrate processing device may be a silicon nitride layer. A plasma atomic layer deposition (PEALD) process may be used to form the silicon nitride layer. As an Si source, a precursor of dichlorosilane (SiH2Cl2), aminosilane, or iodosilane may be used. As a nitrogen source, a nitrogen gas may be used. The nitrogen gas reacts with a physisorbed silicon source on the substrate when activated by plasma, but does not react with the silicon source when not activated by the plasma and may be used as a purge gas.

Referring to FIG. 3 , a group-cycle includes two sub-steps of the first sub-step (Step 1) and the second sub-step (Step 2), and each sub-step may be repeated in a cycles and b cycles, respectively. These sub-steps may be included in a group cycle, which may be repeated. The first sub-step (step1) is a step of uniformly depositing an SiN film on a pattern structure, and the second sub-step (step2) is a plasma treatment step.

During the second sub-step (step2), a bonding structure of an SiN film deposited on an upper surface of the pattern structure in a direction perpendicular to the traveling direction of a radical may be weakened. Therefore, in the second sub-step (Step2), in order to enhance a plasma ion bombardment effect, an atmosphere having a lower process pressure and a higher plasma power may be set as compared with the first sub-step (Step1). After the group-cycle, wet etching on the substrate is performed in a 100:1 diluted hydro fluoride (DHF) solution, and as a result, the SiN film deposited on the upper surface of the pattern structure is removed and an SiN film deposited on a side surface of the pattern remains.

Meanwhile, during the wet etching, not only an SiN film deposited on an upper surface of the stepped structure but also an SiN film deposited on a side surface of the stepped structure are simultaneously etched. However, an etch rate of the SiN film on the upper surface is high, and as a result, the SiN film on the side surface remains. That is, in order to realize an SiN film on a sidewall of a desired thickness, a thicker SiN film needs to be formed when the SiN film is actually deposited. In other words, when the etch rate of the SiN film on the upper surface of the pattern structure is faster, the SiN film on the sidewall may be realized with the same thickness even if a less thick SiN film is formed during deposition. This will save process time and speed up substrate processing per hour. FIG. 5 shows such a process, wherein FIG. 5 (a) shows an SiN film formed on a stepped structure, and FIG. 5 (b) shows an SiN film on a sidewall of the stepped structure remaining after wet etching.

Referring to FIG. 5 (a), the SiN film is deposited to a uniform thickness on the pattern structure (upper film d=side film c in the FIG. 5A). Since a bonding structure of the upper SiN film is broken by the second sub-step (Step 2) of FIG. 3 , the upper SiN film d is etched faster than the side SiN film c during wet etching. The thickness on the side SiN film is also removed to some extent, but the etch rate of the side SiN film is slower than that of the upper SiN film. Therefore, only the side SiN film (a in FIG. 5 (b)) remains after the wet etching (see FIG. 5 (b)). That is, in order to implement a side film of a desired thickness, an additional film b needs to be formed considering an etch rate of the upper film d.

In other words, an etch rate Ed of the upper film d and an etch rate Ec of the side film c determine the selectivity, and the faster the etch rate Ed on the upper surface, the better the selectivity will be. As shown in FIG. 5 , a film (a+b) thicker than the side film a of the desired thickness is deposited considering the difference in the etch rates of the upper film d and the side film c.

FIG. 6 shows a substrate processing method according to the embodiment of FIG. 3 . Referring to FIG. 6 , a first SiN layer a, a second SiN layer b, and a third SiN layer c are sequentially formed according to an atomic layer deposition method. A nitrogen plasma treatment (Step 2) is performed for each layer during one cycle. For the sake of understanding, in this embodiment, three group-cycles GC1, GC2, and GC3 are shown to be performed (x=3), and the nitrogen plasma treatment (Step2) is performed only once for each layer (b=1).

In FIG. 6 , the nitrogen plasma treatment performed for each group-cycle is indicated by an asterisk. The first indication GC1 shows a nitrogen radical applied during a group-cycle of depositing a first layer a, the second indication GC2 shows nitrogen radicals applied during a group-cycle of depositing a second layer b, and the third marking GC3 shows nitrogen radicals applied during a group-cycle of depositing a third layer c.

For example, since the nitrogen plasma treatment is performed by applying a plasma power higher than a critical plasma power, nitrogen radicals destroy the bonding structure of the SiN layer deposited on the upper surface of a pattern. Although nitrogen plasma is applied in the above experiments, the bonding structure of the film may be more easily broken by applying Ar plasma with big and heavy elements.

As shown in FIG. 6 , it should be noted that plasma applied in the second sub-step (Step2), which is a plasma treatment step, when each film are deposited, also affects a lower film. That is, when forming each layer, the nitrogen plasma treatment proceeds only one cycle (b=1) in the second sub-step (Step2) in the group-cycle, but a lower layer is further subjected to plasma treatment. In other words, when sequentially depositing the first layer a, the second layer b, and the third layer c, the first layer a adjacent to a pattern structure is subjected to three plasma treatments, the second layer b on the first layer a is subjected to two plasma treatments, and the third layer c away from the pattern structure is subjected to one plasma treatment. This means that the etching characteristics in the whole bulk film (a+b+c) are not uniform and the WER is higher toward the lower portion of the film (Ea<Eb<Ec).

FIG. 7 shows a change in the wet etch rate in the SiN thin film which is the bulk film according to FIG. 6 . A horizontal axis represents a change in an etching time, and a vertical axis represents a change in an etch rate according to the etching time. The relationship between the horizontal axis and the vertical axis corresponds to a change in the etch rate inside the film from the surface of the bulk film to the inside. As shown in the graph, it can be seen that the etch rate is not uniform from the surface of the SiN thin film to a deep portion. That is, it can be seen that the WER is less at a surface portion of the SiN thin film that is applied with less plasma, and the WER is great at the deep portion of the SiN thin film that is applied with a large amount of plasma by repeating the group-cycle.

When wet etching characteristics of the bulk film are not uniform, the selectivity between an upper surface and a side surface is reduced. For example, when the etch rate of a thin film on the upper surface is less in an initial stage of a wet etching process subsequent to a deposition process, as much of a thin film on the side surface is etched as the film on the upper surface is etched. On the contrary, when the etch rate of the deep portion of the thin film is less in a late wet etching process subsequent to the deposition process, the thin film on the side surface is etched as much while etching the deep portion of the film. As a result, as shown in FIG. 8 , when a thin film on an upper portion of a pattern structure is etched, only a thin film having a thickness e less than or equal to the desired thickness a remains on the side surface, and as a result, the selectivity between an upper thin film and a side thin film is reduced.

Therefore, in consideration of this problem, the thin film needs to be deposited to have a relatively thick thickness in a thin film forming operation. This means that the increased source and gas consumption increases the cost of ownership (COO) of a device and lowers substrate throughput per unit time.

FIG. 9 is a view of a substrate processing method according to embodiments. The substrate processing method according to the embodiments may be a variation of the substrate processing method according to the above-described embodiments. Hereinafter, repeated descriptions of the embodiments will not be given herein.

Referring to FIG. 9 , disclosed is a substrate processing method capable of improving the selectivity in a bulk film by making an etch rate of the bulk film uniform throughout its entire thickness. This substrate processing method may be performed in a direct plasma deposition device composed of upper and lower electrodes, shown in FIG. 4 .

In the embodiment shown in FIG. 9 , the third sub-step (Step 3) for performing post plasma treatment is added as compared to the embodiment of FIG. 3 . First, two sub-steps (Step1 and Step2) are repeated several times. That is, the first sub-step (Step 1) is repeated a cycles, and the second sub-step (Step 2) is repeated b cycles. Then, a group-cycle is performed so that this repetition is repeated several times (x cycle repetition). After a group step is completed, the third sub-step (Step 3) for the post plasma treatment is performed. The post plasma treatment may be repeated several times (e.g., y cycles). Each step will be described in more detail later below.

1. First Sub-Step (Step 1): Conformal Deposition

This step is a step of depositing an SiN film on a pattern as the first sub step. Since the SiN film of a uniform thickness is deposited, thicknesses of SiN films deposited on an upper portion and a side portion of the pattern are the same. A source gas of halide series (e.g. dichlorosilane (DCS)) or aminosilane or iodosilane series may be used as a silicon source, and a nitrogen gas may be used as a nitrogen source. The nitrogen gas, when activated with plasma, reacts with the silicon source to be the component of a film, but may be used as a purge gas without reacting with the silicon source when not activated with plasma.

During the first sub-step, the SiN film is uniformly applied on a pattern structure while the source gas, a reactor gas, and the plasma are alternately supplied and repeated several times (a cycles) by a PEALD method. A plasma power is weakened to allow radicals to be supplied to the inside of the pattern. The plasma power is supplied from 200 watts to 900 watts, preferably 500 watts.

In addition, by increasing process pressure to weaken straightness of the radicals to allow more radicals to be supplied to a pattern side surface than a pattern bottom surface, thereby facilitating formation of the SiN film on the side portion. In this step, process pressure of about 10 Torr to about 20 Torr is maintained.

2. Second Sub-Step (Step 2): Cyclic Plasma Treatment

This step is a step of performing nitrogen plasma treatment on the SiN film deposited on the pattern as the second sub step. In particular, this step is to increase the etch selectivity between a film deposited on an upper surface and a side surface. As described above, a plasma power above a critical plasma power is applied to break a bonding structure of the film on the upper surface of a pattern structure in a direction perpendicular to the direction of radical progression, whereby the etch rate of a thin film on the upper portion is higher than that of a thin film on the side portion.

In the disclosure, although nitrogen gas which is the same as the component of the film is used, the heavier element Ar gas may be used to more easily break the bonding structure of the film. In this step, plasma treatment is performed at a plasma power of about 700 watts to about 1000 watts, preferably about 700 watts higher than in the first sub-step (Step 1) to enhance radical straightness and an ion bombardment effect.

In addition, in order to strengthen the ion bombardment on the upper and lower surfaces rather than the pattern side, the process pressure is set lower than the pressure of the first sub-step (Step 1). In the disclosure, the plasma treatment is performed at process pressure of about 1 Torr to about 5 Torr, preferably about 3 Torr. This step is also repeated several times (b cycles). In addition, the group step that combines the first sub-step and the second sub-step is repeated several times (x cycles).

3. Third Sub-Step (Step 3): Post Plasma Treatment

This step is to solve the problem of non-uniform wet etching characteristics in the SiN thin film. In this step, a hydrogen gas is added to activate a mixed gas of nitrogen and hydrogen with an RF power. In order to facilitate the penetration of radicals into the film on the upper and lower surfaces of the pattern, the process pressure is lower than the deposition step (Step 1) and the plasma power is higher than the deposition step (Step 1). This step is performed at a plasma power of 700 watts to 1000 watts, preferably 700 watts higher than a plasma power of the deposition step (Step1) to enhance the radical straightness and the ion bombardment effect.

In addition, the process pressure is set lower than the deposition step (Step1) in order to strengthen the ion bombardment on the upper and lower surfaces rather than the pattern side. In the disclosure, the plasma treatment is performed at process pressure of about 1 Torr to about 5 Torr, preferably about 3 Torr. Hydrogen radicals form weak bonding with the SiN thin film or weaken the bonding structure of the SiN thin film, and an effect of weakening the bonding structure by the hydrogen radicals is maximized on a surface directly subjected to the plasma treatment. Therefore, etching resistance of a film surface may be weakened.

In addition, by supplying nitrogen radicals together, the ion bombardment of the SiN thin films on the upper and lower surfaces and the resulting weakening of the bonding structure are enhanced. In the disclosure, although smaller and lighter hydrogen than other elements is used, helium may also be used. In another embodiment, only hydrogen gas may be supplied without supplying nitrogen gas.

Table 1 below shows exemplary experimental conditions applied to each step.

TABLE 1 First sub-step Second sub-step Third sub-step (Step 1) (Step 2) (Step 3) Gas flow Si source 1000~5000 0. 0. (sccm) (Carrier N2) Reactant N2  5000~20000 1000~20000   0~20000 H2 0. 0.  20~1000 Process Source feed 0.1~0.7 0. 0. time Purge 0.5~1.0 0. 0. (sec)/cycle Plasma 3.0~5.0 3~60 3~60 Purge 0.1~0.3  0~1.0  0~1.0 Plasma RF Power 200~900 700~1000 700~1000 (W) Freq. 13.56 MHz   100 kHz~13.56 MHz   100 kHz~13.56 MHz Pressure (Torr) 10~20 1~5  1~5  Heater Temp (° C.) 300~550 300~550  300~550 

By applying the process conditions shown in Table 1 above, it is possible to improve the etch selectivity between films deposited on the upper surface and the side surface of a pattern when depositing a thin film on a pattern structure. In addition, through a process of depositing a uniform film on the pattern by a PEALD method (first sub-step (Step 1)), a process of breaking a bonding structure of the film on the upper surface of the pattern (second sub-step (Step 2)), and a process of implementing uniform etching characteristics and a high etch rate (third sub-step (Step 3)), it is possible to achieve higher etch selectivity more efficient for an RTS process than in the conventional technology.

FIG. 10 is a graph showing etching characteristics of a thin film after a process according to the disclosure. As shown in FIG. 10 , when the conditions according to the disclosure are applied, that is, when the first to third sub-steps (Step1+Step2+Step3) are performed, the WER is constant regardless of time. That is, it is possible to secure a constant WER regardless of the position in the SiN thin film.

Meanwhile, in the case of an embodiment of the first and third sub-steps (Step1+Step3), it can be seen that, although hydrogen radicals (H2 post PT) supplied during the third sub-step are effective in breaking the bonding structure of a thin film surface, a bonding structure of a deep portion of the thin film is not changed so that the WER decreases over time.

In the case of an embodiment of the first and second sub-step (Step1+step2), it can be seen that, although nitrogen radicals (N2 cyclic PT) supplied during the second sub-step are effective in breaking the bonding structure of the deep portion of the thin film, the bonding structure of the thin film surface is not changed so that the WER is low at the beginning of etching, which reduces the etch selectivity.

Therefore, according to embodiments of the inventive concept, by combining the ion bombardment effect (N2 cyclic PT) by the nitrogen radicals along with the weakening of etching resistance of the thin film surface (post PT) by the hydrogen radicals, the etch rate may be further improved by further weakening the etching resistance over the entire thickness of an upper thin film.

TABLE 2 N2 cyclic PT N2 cyclic PT + Post PT Bottom/Side 6.3. 21.5. Etch selectivity

Table 2 shows results of the etch selectivity of the SiN thin film in a wet etching time of 80 seconds in the embodiment of FIG. 10 . Etching is performed in a 100:1 DHF solution. According to FIG. 10 and Table 2 above, the result according to the disclosure is increased to 21.5 compared to 6.3 which is the result of cyclic plasma treatment (N2 Cyclic PT) using the nitrogen radicals, thereby improving the selectivity up to 3.4 times or more. That is, by additionally performing the plasma treatment (Post PT) using hydrogen-mixed gas (Post PT) in addition to cyclic plasma treatment (N2 Cyclic PT) using the nitrogen radicals, the etching resistance of the film surface on the pattern structure is weakened, and then an upper surface film may be etched at a uniform and high etch rate. That is, a thicker film may be left on the side of the pattern structure, so that efficient process performance may be achieved.

FIG. 11 schematically shows the results of Table 2 above. It can be seen that the etch selectivity is much improved (see FIG. 11B) by performing the first to third sub-steps (step1+step2+step3) according to the disclosure. In a case where only the first and second sub-steps are performed, a side surface film remains below a desired thickness while the upper surface film is etched entirely (see FIG. 11A). However, when the first to third sub-steps (Step1+Step2+Step3) are performed, a film of the desired thickness remains.

FIG. 12 is a view of a substrate processing method according to embodiments. The substrate processing method according to the embodiments may be a variation of the substrate processing method according to the above-described embodiments. Hereinafter, repeated descriptions of the embodiments will not be given herein.

Referring to FIG. 12 , a source gas may be supplied during the third sub-step (Step3). In this step, the SiN thin film is further deposited by supplying the source gas. However, since a high plasma power is supplied during the third sub step, the ion bombardment effect becomes dominant, and the density of the newly deposited SiN thin film on an upper surface is weakened. Meanwhile, the newly deposited SiN thin film on the side surface has a relatively weak ion bombardment effect and a relatively high density.

In addition, since a low pressure atmosphere is formed during the third sub-step, the ion bombardment effect is applied to a bottom surface of the pattern structure in addition to the upper surface. That is, since the density of the newly deposited SiN thin films on the top and bottom surfaces is weakened, and the density of the SiN thin film on the side surface is relatively increased, the etch selectivity may be improved in a subsequent isotropic etching operation (e.g., wet etching operation).

FIG. 13 is a view of a substrate processing method according to embodiments. The substrate processing method according to the embodiments may be a variation of the substrate processing method according to the above-described embodiments. Hereinafter, repeated descriptions of the embodiments will not be given herein.

Referring to FIG. 13 , operation S310 of forming a first layer is performed. The first layer may be formed to have a uniform thickness on a pattern structure. The first layer may include a plurality of layers, and the plurality of layers may be formed by repeatedly performing a cycle of an atomic layer deposition process. For example, the first layer may be an insulating layer.

Thereafter, operation S320 of changing a characteristic of a portion of the first layer is performed. For example, a bonding structure of a portion of the first layer may be changed by applying directional energy under a first process condition. In more detail, first plasma of the first processing condition may be applied in a direction substantially perpendicular to the first layers formed on the upper and lower surfaces of the pattern structure, and due to the first plasma, a bonding structure of portions formed on the upper and lower surfaces of the pattern structure of the first layer may be changed.

Thereafter, operation S330 of forming a second layer on the first layer is performed. In an example, at least one layer may be inserted between the first layer and the second layer. The second layer may be formed to have a uniform thickness on the first layer. The second layer may include a plurality of layers, and the plurality of layers may be formed by repeatedly performing a cycle of an atomic layer deposition process. For example, the second layer may be formed of the same material as the first layer.

Thereafter, operation S340 of changing characteristics of portions of the first layer and the second layer is performed. For example, a bonding structure of the portions of the first layer and the second layer may be changed by applying the directional energy under the first process condition. In more detail, second plasma of the first processing condition may be applied in a direction substantially perpendicular to the second layers formed on the upper and lower surfaces of the pattern structure, and due to the second plasma, a bonding structure of portions formed on the upper and lower surfaces of the pattern structure of the first layer and portions formed on the upper and lower surfaces of the pattern structure of the second layer may be changed.

Thereafter, operation S350 of reducing a difference between the characteristics of a portion of the first layer and the characteristics of a portion of the second layer is performed. When the above-described characteristic change operations are repeated, the lower layer receives energy in duplicate, resulting in a difference in characteristics between the upper layer and the lower layer. For example, the degree of change in a bonding structure of a portion of the lower first layer may be greater than the degree of change in a bonding structure of a portion of the upper second layer. Thus, additional operation S350 may be performed to reduce the difference between characteristics of a portion of the first layer and characteristics of a portion of the second layer.

As an example of the additional operation S350, energy (e.g., third plasma) may be applied in a direction substantially perpendicular to the second layers formed on the upper and lower surfaces of the pattern structure, and the energy may further change the bonding structure of portions formed on the upper and lower surfaces of the pattern structure of the second layer. In more detail, the bonding structure of a portion of the second layer may be changed by applying directional energy under a second process condition.

The second process condition is different from the first process condition used in the above-described characteristic change operations, and in particular, the second process condition may be set so as to affect only the bonding structure of the second layer without affecting the bonding structure of the first layer. That is, the first process condition may be used during the application of the first plasma and the application of the second plasma, and the second process condition that is different from the first process condition may be used during the application of the third plasma.

By applying the third plasma using the second process condition, only the bonding structure of the upper second layer may be changed without changing the bonding structure of the lower first layer. Therefore, a difference between the degree of change in the bonding structure of a portion of the lower first layer and the degree of change in the bonding structure of a portion of the upper second layer may be reduced.

FIG. 14 is a view of a substrate processing method according to embodiments. The substrate processing method according to the embodiments may be a variation of the substrate processing method according to the above-described embodiments. Hereinafter, repeated descriptions of the embodiments will not be given herein.

Referring to FIG. 14 , operation S510 of repeating a cycle to form a thin film is performed. The thin film may include, for example, a nitride film, specifically, a silicon nitride film. The cycle may include supplying a first gas (e.g., a source gas) onto a substrate and supplying a second gas (e.g., a reaction gas) that is reactive with the first gas.

During the repetition of the cycle, energy may be applied. Due to the repeated application of the energy, a first portion of the thin film adjacent to the substrate may have a higher WER than that of a second portion of the thin film away from the substrate. That is, in the thin film adjacent to the substrate, the energy is repeatedly applied during the thin film formation, thereby increasing the WER. However, the thin film away from the substrate may be energized only a limited number of times in a latter part of the thin film formation, and thus the WER may not increase.

Therefore, additional operation S520 of offsetting such differences in WER may be performed. That is, operation S520 of reducing the difference between the WER of the first portion and the WER of the second portion may be further performed. For example, by setting process conditions such that energy may be applied to portions adjacent to an exposed surface of the thin film, the WER of portions adjacent to the exposed surface of the thin film (i.e., the second portion) may be increased. As a result, variation of WER by location of the thin film caused by the cycle repetition may be reduced, and during the subsequent wet etching operation S530, a uniform WER may be achieved over the entire thickness range of the thin film.

FIG. 15 shows an SiN thin film shape on a stepped structure according to a thin film etch rate of the above-described substrate processing methods. FIG. 15 (a) shows the shape of a thin film before a wet etching state. A thin film of a certain thickness is uniformly deposited on the stepped structure.

FIG. 15 (b) shows an example of depositing and wet etching a thin film using the first sub-step and the second sub-step. Since etch rates of upper and lower portions of the stepped structure at the beginning of the wet etching are low, an over-etch rate needs to be increased to remove both upper and lower films of the stepped structure, and thus the film on the side of the stepped structure becomes thinner. Therefore, when a side film of a certain thickness is required, a deposition thickness of the film needs to be increased and productivity is reduced.

FIG. 15 (b) shows an example of depositing and wet etching a thin film using the first sub-step and the third sub-step. The etch rate is high only at the beginning of the wet etching, and as the etching proceeds, the etch rate rapidly decreases and converges to a certain value. Therefore, a patterning process is possible only when the thickness of a side film is thin, and when the thickness of the side film is thick, the thin film remains on the upper and lower portions of a stepped structure.

FIG. 15 (d) shows an example of depositing and wet etching a thin film using the first sub-step, the second sub-step, and the third sub-step according to embodiments of the inventive concept. Since the etch rate is constant and high over time, the upper and lower films of a stepped structure may be etched in a short time to reduce side film loss. In addition, since the thickness of a side film remaining after the wet etching becomes greater, the applications in which the process can be applied may be expanded.

FIG. 16 is a view illustrating a substrate processing method according to embodiments. The substrate processing method according to the embodiments may be a variation of the substrate processing method according to the above-described embodiments. Hereinafter, repeated descriptions of the embodiments will not be given herein.

Referring to FIG. 16 , the substrate processing method may include forming at least one layer (S110), applying plasma under the first process condition (S120), applying plasma under a second process condition different from the first process condition (S150), and purging plasma under the second process condition (S155), followed by an isotropic etching operation (S160). Here, the plasma purging refers to purging plasma products, such as ions or radicals generated by plasma. The plasma purging operation (S155) may correspond to step t8 of FIG. 9 .

By performing the operation (S155) of plasma purging under the second process condition, etch selectivity of a thin film formed on a pattern structure may be improved. In more detail, the operation (S150) of applying plasma is performed to change a bonding structure of a portion of a thin film on the pattern structure, and activated ions or radicals remain between pattern structures. By performing the operation (S155) of plasma purging, plasma products remaining between the pattern structures may be removed.

In some embodiments, a hydrogen-containing gas may be supplied during the applying of plasma under the second process condition. In this case, the hydrogen-containing gas may be removed from a reaction space during the operation (S155) of plasma purging under the second process condition. A hydrogen gas weakens the bonding structure of the thin film on the pattern structure, but is also supplied between the pattern structures and affects a film deposited on the side of the pattern structure to some extent. The hydrogen gas remaining between these pattern structures may be an inhibitory factor in improving the etch selectivity. Therefore, by carrying out the plasma purging under the second process condition (S155), and by removing hydrogen remaining between the pattern structures, it is possible to improve the etch selectivity by minimizing the effect of the hydrogen gas on the thin film on the side of the pattern structure.

In some embodiments, the applying of plasma under the second process condition (S150) and the plasma purging under the second process condition (S155) may be performed in one cycle. That is, one cycle including operations (S150 and S155) may be repeated a plurality of times such that a thin film satisfying a certain condition is formed.

FIG. 17 shows the degree of wet etching of the thin film on the sidewall of the pattern structure according to the presence or absence of the above-described plasma purging under the second process condition (S155). FIG. 17 a shows a case where there is no plasma purging operation, and FIG. 17 b shows a case where a plasma purging operation is added.

Referring to FIG. 17 a , a thin film is formed on the pattern structure without performing a plasma purging. As a result of performing wet etching for 5 minutes without performing a plasma purging after processing plasma under the second process condition, thin films on upper and lower portions of the pattern structure are removed, and the thickness of the thin film on the sidewall of the pattern structure decreases from 135 angstroms to 113 angstroms. That is, it can be seen that a wet etch rate of 4.4 Angstroms per minute is achieved.

On the other hand, in the case of FIG. 17 b in which a plasma purging operation is added, it can be seen that the wet etch rate is lower. After forming a thin film on the pattern structure, plasma processing under the second process condition is performed, and then the plasma purge is carried out. After 5 minutes of wet etching, thin films on upper and lower portions of the pattern structure are removed, and the thickness of the thin film on the sidewall of the pattern structure decreases from 142 angstroms to 130 angstroms. That is, it can be seen that a wet etch rate of 2.4 Angstroms per minute is achieved.

As such, a hydrogen gas around the sidewall between the pattern structures is removed through the purging operation, so that the influence of the hydrogen gas on the sidewall may be minimized. As a result, the weakening of a bonding structure of the thin film on the sidewall is prevented, and a technical effect of realizing high etch selectivity may be achieved.

During the plasma purging under the second process condition (S155), a nitrogen gas may be used as a purge gas. That is, plasma products such as ions and radicals may be purged by supplying and exhausting the nitrogen gas into a reaction space. In some embodiments, during the plasma purging under the second process condition (S155), vacuum purge may be applied without a separate purge gas. In another embodiment, during the plasma purging under the second process condition (S155), the nitrogen purge gas and the hydrogen gas may be supplied together. By supplying the nitrogen purge gas and the hydrogen gas together, pressure fluctuation may be reduced to more stably carry out the process.

Table 3 below shows a wet etch rate in each portion of the pattern structure according to the presence or absence of the above-described plasma purging under the second process condition (S155).

TABLE 3 no purge operation purge operation (S155) (S155) wet etch rate upper portion 73.6 58.9 (WER) side portion 13.4 3.1 (Å/min) lower portion 68.7 63.8 etch selectivity on upper 5.5 19.0 portion/side portion

When the purge operation is added in Table 3 above, as the hydrogen gas is removed from the reaction space, the etch rate is lowered overall, but it can be seen that etch selectivity between a film on the sidewall and a film on the upper surface of the pattern structure is significantly improved compared to the case having no purge operation.

As described above, according to the disclosure, by adding a purge operation to a hydrogen plasma processing operation and removing a hydrogen gas remaining near a sidewall between pattern structures, there is a technical effect that may improve etch selectivity between upper and side surfaces of the pattern structures.

It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the following claims. 

What is claimed is:
 1. A substrate processing method comprising: forming a thin film on a substrate by performing a plurality of cycles, each cycle comprising a layer-forming plasma treatment including forming at least one layer and a layer characteristic-changing plasma treatment including applying plasma to the at least one layer under a first process condition to change a bonding structure of a portion of the thin film; applying plasma to the thin film under a second process condition different from the first process condition to further change the bonding structure of a portion of the thin film while maintaining an overall structure of the thin film; and isotropically etching the overall structure of the thin film, wherein the layer characteristic-changing plasma treatment is repeated during the plurality of cycles and the applying plasma to the thin film is performed after the plurality of cycles.
 2. The substrate processing method of claim 1, setting an atmosphere such that plasma ions have directionality during the applying of plasma under the first process condition and the applying of plasma under the second process condition.
 3. The substrate processing method of claim 1, wherein, in each cycle of the plurality of cycles, the layer-forming plasma treatment is performed a plurality of times as a sub-cycle, and the layer characteristic-changing plasma is performed after the sub-cycle, and wherein the layer-forming plasma is performed under a process condition different from the first process condition and the second process condition.
 4. The substrate processing method of claim 1, wherein etch selectivity between the portion where the bonding structure of the thin film is changed and the remaining portion of the thin film is achieved during the step of isotropically etching.
 5. The substrate processing method of claim 1, wherein the at least one layer is formed on a stepped structure having an upper surface, a lower surface, and a side surface between the upper surface and the lower surface, and the portion of the thin film corresponds to a portion of the thin film formed on the upper surface and the lower surface.
 6. The substrate processing method of claim 5, wherein repetition of the cycles causes a difference between a first bonding structure of a first portion of the thin film adjacent to the stepped structure and a second bonding structure of a second portion of the thin film away from the stepped structure, and during the applying of the plasma under the second process condition, the difference between the first bonding structure of the first portion and the second bonding structure of the second portion is reduced.
 7. The substrate processing method of claim 5, wherein after the step of isotropically etching, thin films on the upper surface and the lower surface of the stepped structure are removed, and a thin film on the side surface of the stepped structure remains.
 8. The substrate processing method of claim 1, wherein a hydrogen-containing gas is supplied during the applying of the plasma under the second process condition.
 9. The substrate processing method of claim 1, wherein the forming of the at least one layer comprises: supplying a first gas; purging the first gas; and supplying a second gas and applying plasma to form a first layer.
 10. The substrate processing method of claim 9, wherein pressure in a reaction space is maintained at a first pressure during the supplying of the second gas and the applying of the plasma to form the first layer, and the pressure in the reaction space is maintained at a second pressure lower than the first pressure during the applying of the plasma under the first process condition.
 11. The substrate processing method of claim 9, wherein power supplied during the applying of the plasma under the first processing condition is greater than power supplied during the supplying of the second gas and the applying of the plasma to form the first layer.
 12. The substrate processing method of claim 9, wherein the first gas is supplied during the applying of the plasma under the second process condition that is different from the first process condition.
 13. The substrate processing method of claim 9, wherein, during a first cycle, the supplying of the first gas, the purging of the first gas, and the supplying of the second gas and applying of plasma to form the first layer are performed a plurality of times.
 14. The substrate processing method of claim 13, wherein, during the first cycle, the plasma under the first process condition is applied to the first layer so that a WER of a portion of the first layer increases due to an ion bombardment effect of plasma ions.
 15. The substrate processing method of claim 14, wherein forming of a second layer on the first layer during a second cycle after the first cycle is performed, wherein the forming of the second layer comprises: supplying a first gas; purging the first gas; and supplying a second gas and applying plasma to form the second layer.
 16. The substrate processing method of claim 15, wherein, during the second cycle, the plasma under the first process condition is applied to the second layer and the first layer which is below the second layer so that WERs of a portion of the first layer and a portion of the second layer increase due to an ion bombardment effect of the plasma ions, wherein the WER of the first layer is greater than the WER of the second layer.
 17. The substrate processing method of claim 16, wherein the plasma under the second process condition is applied toward the first layer and the second layer, and thus a difference between the WER of the first layer and the WER of the second layer is reduced.
 18. The substrate processing method of claim 1, further comprising: purging the plasma products under the second process condition.
 19. A substrate processing method comprising: a first layer-forming plasma treatment including forming a first layer; a first layer characteristic-changing plasma treatment including applying first plasma to the first layer to change characteristics of a portion of the first layer; a second layer-forming plasma treatment including forming a second layer on the first layer; a second layer characteristic-changing plasma treatment including applying second plasma to the first layer and the second layer to change characteristics of respective portions of the first layer and the second layer; applying third plasma to the second layer to reduce a difference between the characteristics of a portion of the first layer and the characteristics of a portion of the second layer while maintaining an overall structure of the first layer and the second layer; and isotropically etching the overall structure of the thin film, wherein the applying third plasma to the second layer is performed after the first layer-forming plasma treatment, the first layer characteristic-changing plasma treatment, the second layer-forming plasma treatment, and the second layer characteristic-changing plasma, wherein the applying third plasma to the second layer is performed between the second layer characteristic-changing plasma treatment and the step of isotropically etching the overall structure of the thin film and wherein a first process condition is used during the application of the first plasma and the application of the second plasma, and a second process condition that is different from the first process condition is used during the application of the third plasma. 